The proposed study is a continuation and extension of a current study investigating the phonological knowledge and learning patterns of speech disordered children. Research techniques and findings from linguistic theory, speech science and speech pathology are combined in an interdisciplinary investigation of both normal and disordered sound systems. The findings from this study will have both theoretical and applied significance to both phonological theory and speech pathology. Project I will continue to investigate the phonological systems of the 40 children from the current grant. Three specific studies are proposed: (1) Post-hoc, finer grained analyses will be made of individual subjects' learning patterns of specific sounds to determine the relationship between sounds in terms of feature dependencies, phonological knowledge and training. (2) Longitudinal acoustic analyses will be made to show the change in acoustic parameters over time. (3) A subgroup of the most severly disordered children will receive continued treatment to determine the critical point for phonological restructuring. Project II includes two studies examining the phonological and acoustic characteristics of normally developing speech at three points across one year. The acoustic analyses should complement the phonological analyses and the two sets of analyses should provide a basis for comparison with the speech disordered population cross-sectionally and longitudinally (c.f. the results from the current grant and Project I). Project III includes two experimental studies which will focus on the roles of stimulability and consonant cluster training as possible factors in predicting generalization patterns.